Well production testing and flow characteristic evaluation methods using small diameter tubing

ABSTRACT

Well methods using small diameter tubing introduced into and withdrawn from the well by an injector apparatus. The tubing is introduced into and withdrawn from the well by the injector from a tubing-holding reel. The methods include the introduction of an inert gas such as nitrogen through the small diameter tubing. Other gases may also be introduced through the small diameter tubing. The methods are especially suitable for use in petroleum wells, but may if suitable be used in water wells. The small diameter tubing is hung in the well with its lower end adjacent the formation to be tested, and injection of gas through the tubing lifts a layer of uncontaminated reservoir fluid to the surface. Continued gas injection accomplishes formation flow characteristic evaluation.

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United States Patent 1 Smith et al.

[54] WELL PRODUCTION TESTING AND FLOW CHARACTERISTIC EVALUATION METHODS USING SMALL DIAMETER TUBING [76] Inventors: Arthur W. Smith; Ray A. Plummer; Charles Wayne Johnson, all of P. O. Box 3047, Houston, Tex. 77001 [22] Filed: Apr. 28, 1971 [21] App]. No.: 138,140

Related U.S. Application Data [62] Division of Ser. No. 873,932, Nov. 4, 1969, aban- 111 3,722,589 [451 Mar. 27, 1973 Primary ExdminerStephen J. Novosad Attorney-Carl B. Fox, Jr.

57 ABSTRACT Well methods using small diameter tubing introduced into and withdrawn from the well by an injector apparatus. The tubing is introduced into and withdrawn from the well by the injector from a tubing-holding reel. The methods include the introduction of an inert gas such as nitrogen through the small diameter tubing. Other gases may also be introduced through the small diameter tubing. The methods are especially suitable for use in petroleum wells, but may if suitable be used in water wells. The small diameter tubing is hung in the well with its lower end adjacent the formation to be tested, and injection of gas through the tubing lifts a layer of uncontaminated reservoir fluid to the surface. Continued gas injection accomplishes formation flow characteristic evaluation.

8 Claims, 4 Drawing Figures PATENTEUmzmza 3,7 2,5 9

sum 10F 2 INVENTORS ATI'O/P/VEV PATENTEDHARZHQB SHEET 2 BF 2 WELL PRODUCTION TESTING AND FLOW CHARACTERISTIC EVALUATION METHODS USING SMALL DIAMETER TUBING This application is a division of application Ser. No. 873,932, filed Nov. 4, I969, and entitled Well Methods Using Small Diameter Tubing now abandoned.

BACKGROUND OF THE INVENTION Injection equipment has relatively recently become available through use of which tubing strings may be in troduced into and withdrawn from wells. Such equipment has been developed for use with tubings of /4 inch to l inch diameter size. Apparatus has not been available for introduction of steel tubing of smaller than 3'4 inch diameter. However, the equipment which is available may be converted for introduction of the smaller size tubing. According to this invention, /5 inch to inch outside diameter steel tubing is the preferred size for use, although larger or smaller sizes may be used. According to this invention, use of smaller inexpensive tubing is feasible for introduction of gases into wells for various treatment purposes.

Exemplary of the types of tubing injection apparatuses which are available are those disclosed in US. Pat. Nos. 3,182,877, 3,285,485, 3,258,110, 3,330,531, and 3,379,393. Such apparatuses have not been developed or used in connection with methods such as those herein described.

A primary object of the invention is to provide methods for performing well treatments and operations using small diameter tubings injectable and withdrawable from a well, and for production testing and flow characteristic evaluation of the well.

The methods afforded according to the invention are very economical. The small diameter tubing used is of relatively low cost and may be used for long periods of time in a single well or may be used over and over in the same or different wells, as the apparatus employed in connection with the methods is entirely portable. The methods avoid the use of workover rigs and tools where the same would otherwise be required. The methods may be performed very rapidly without lengthy shut downs or delays being necessary.

Other objects and advantages of the invention will appear from the detailed descriptions of preferred embodiments of the invention and from the accompanying drawings illustrating the methods.

BRIEF DESCRIPTIONS OF THE DRAWINGS FIG. 1 is a schematic showing of a displacement method of preferred form according to the invention, and an apparatus useful therewith.

FIGS. 1A 1B are partial schematic showings illustrating, respectively, progressive fluid displacement and backwash steps of the method of FIG. I. 7

FIG. 2 is a partial schematic showing illustrating methods for production sampling and testing according to the invention.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS Referring first to FIG. 1 of the drawings, a well 10 has therein one or more casings ll lining the well hole, and may have other pipes, casings, or tubings therein as required for the purposes of the well, all as well known in the art. Above the well, there is provided a well head 12 which may be of any form employed in the art, the well head including devices for suspending pipes in the well, valves for controlling well pressures, and valvecontrolled outlets for providing for flow to and from the pipes in the well. Above the well head, there is a blowout preventer 15, or other device through which a pipe string may be run without leakage of pressures from within the well. The blowout preventer, or seal, about the small diameter tubing may take the form of a hydraulically activated rubber or elastomeric packoff.

Above the blowout preventer or packoff there is disposed a tubing injector device 17 which may be of any of the forms available in the art, but modified for use with smaller than conventional size tubing, and capable of rapidly running the tubing into a well and withdrawing the tubing from the well. Injector 17 is modified for use with, for example, 1% inch steel tubing. The tubing lengths are welded together at their ends and have no exterior projections. Above the injector 17 there is provided a curved tubing guide 18. The tubing guides are usually provided with a plurality of rollers rotatable between side guide elements to guide the tubing through a curve or bend when moved longitudinally. Apparatus of the type shown and described in the drawings, of Bowen Tools, Inc., is shown and described in THE OIL AND GAS JOURNAL, Jan. I3, 1964, at pages 72-73. Other equipment for the same purposes is produced by Brown Oil Tools, Inc. v

The tubing injector is supported by a frame 20'which has legs resting upon the ground about the well head. The tubing is stored on a reel 22, and the 'reel is equipped so that introductions of fluid to and from the tubing may be made through the reel hub, while all or part of the length of the tubing is wound on the reel or unwound from the reel and injected into a well. The reel 22 is customarily mounted upon a skid unit which may be set on the ground and may be carried on a truck 23 so as to be movable from job to job. As shown in FIG. 1, a liquid nitrogen and a heater 29 to which liquid nitrogen is pumped by a pump 30, pressured nitrogen gas being obtained by this cryogenic operation. Liquid nitrogen is first pressured by pump or compressor 30 and is then passed to heater 29 for vaporization whereupon high pressure nitrogen gas is delivered through conduit 32 to the tubing 33 by way of the hub flow connections of reel 22. Pressured gas exceeding 10,000 pounds per square inch may be obtained in this manner. Other gas may be used for some methods, but nitrogen is safer because of its non-combustible, inert, nature.

In most cases the well 10 will contain a liquid which extends to a level 36 in the well. For displacement of the liquid from the well, the end 33a of tubing 33 is injected into the well by injector 17 to a position somewhat below liquid surface 36. The liquid in the well may be of any form, such as drilling fluid, oil, water, or the like. As the lower end 33a of tubing 33 moves downwardly in the well gaseous nitrogen is continuously introduced at a rate so as to purge and circulate incremental portions of the liquid upwardly from the well through the annulus of a well pipe such as casing 11, through which the tubing 33 is shown introduced. The liquid in the well may be circulated upwardly through any flow passage in the well through which the gas introduced has access. The liquid circulated out of the well is evacuated through an outlet 38 of the well head. Once the lower end of tubing 33 reaches the bottom of the well, substantially all liquid in the well will have been circulated from the well by the procedure described. Gas introduction may be continuous or discontinuous. It may at times be found beneficial to introduce gas non-continuously and to circulate liquid from the well intermittently when the gas is being introduced. The pressure of gas introduced is adjusted to be sufficient to efficiently force the fluid from the well.

After the fluid has been removed from the well, a pressure draw down exists on the reservoir at the lower portion of the well, the reservoir being denoted by reference numeral 40. Suitable casing perforations 41 are provided at the area of formation or reservoir 40 so that fluid communication from the well may exist. By pressure draw down as mentioned above, it is meant that the pressure within the well is reduced so as to be lower than the reservoir pressure.

The nitrogen gas introduced through tubing 33 may be made to flow outwardly from the well through perforations 41 into the reservoir by closing the upward flow path at the top of the well. When the inert gas pressure within the well is released, the nitrogen which has penetrated the reservoir formation returns to the well and cleans materials such as formation fines, precipitats, scale, shale, contaminants, sand, drilling fluids, filtrates, reservoir fluids, fluid loss control agents, or any chemical, fluid or solid that may be present in the reservoir through the perforations to be carried to the surface and out of the well.

A pressure differential is created with the aid of nitrogen and is essential for removing the hydrostatic column of fluid that restricts reservoir fluid entry to the formation face or well bore perforations. If necessary or desired, nitrogen may be continuously or intermittently introduced through tubing 33 as the tubing is withdrawn upwardly out of the well so that continual evacuation of fluids above the lower end of the tubing from the well is performed. FIG. 1A illustrates progressive fluid removal from a well, and FIG. 18 illustrates the backwash step with return of nitrogen from the formation and up through the well.

As has been stated, use of small diameter tubing strings, smaller than heretofore contemplated in connection with tubing injection equipment, has been found to be advantageous. The tubing lengths are welded together end to end so that the tubing is smooth and uniform inside and outside. The tubing sizes contemplated are sizes up to V4 inch nominal tubing sizes, nominal 55 inch tubing being advantageous for practice of all methods herein described. While 56 inch tubing or smaller tubing is not usually practical for use in conveying liquids into and out of wells because of the poor flow rates and high pressure drops encountered, A inch tubing or even smaller tubing is adequate for flow of high pressure gases into (and out of) wells for the purposes of this invention. For example, it has been found that the pressure drop through 10,500 linear feet of 9% inch tubing at a flow rate of 485 cubic feet of gas (N per minute is about 6,350 pounds per square inch. But since gas pressures upwards of 10,000 pounds per square inch are available, this pressure drop is not excessive. If water were used instead of gas, pressure drops of the order of 15,000 psi would be encountered. For the methods herein described, gas input rates exceeding 200 cubic feet per minute will not normally be required, but gas input rates as high as 600 cubic feet per minute may be employed with k inch tubing without excessive pressure drops as would occur if water were used.

The cost of 9% inch tubing is considerably smaller then the costs of inch and 1 inch tubing heretofore used with tubing injection apparatuses, and the tubing reels for 5: inch tubing are smaller and less costly.

As will be realized, various combinations of the described procedures may be practiced in order to achieve the desired treatment of the well, and the exact procedural combinations are exemplary of the various combinations of procedure steps which may be used to gain the benefits of use of the small diameter tubing strings. It will of course be realized that the tubing strings may be injected, withdrawn, and re-injected, as necessary to the object at hand.

Referring to FIG. 2 of the drawings, the small diameter tubing herein described is used for methods for production testing a reservoir when a' sample of reservoir fluid is required at the surface in an uncontaminated state for formation evaluation. The tubing 33 is injected into the well by injector 17 after the well casing 11 has been perforated as shown at 41 of FIG. 2. Tubing 33 is hung at a tubing hanger 55 provided for that purpose, the wellhead, only a portion of which is shown, having a valved outlet 64 therefrom having flow communication with the well tubing 57. The lower end of tubing 33 is positioned adjacent the perforated area, and hung. Injection of nitrogen downwardly through tubing 33 results in lifting a layer of reservoir fluid 61 entering the well from the formation to the surface and out through outlet 64. The nitrogen injection may be continued sufficiently long to determine the flow characteristics into the well from the reservoir so that production evaluation may be accomplished.

While preferred embodiments of the invention have been shown in the drawings, and described, many modifications thereof may be made by a person skilled in the art without departing from the spirit of the invention, and it is intended to protect by Letters Patent all forms of the invention falling within the scope of the following claims:

We claim:

1. Method for performing production testing of wells, comprising running a small diameter tubing down a well by means of a tubing injector apparatus, said tubing injector apparatus including a reel for storing the tubing wound thereon and having gas entrance means to said tubing at the hub of said reel, said tubing 'being run to below the surface of production entering the well from a reservoir, and production testing the well by injecting pressured gas into the production through said small diameter tubing to lift a portion of said production to the surface for recovery in uncontaminated condition.

2. Method according to claim 1, said pressured gas being nitrogen.

3. Method according to claim 1, including continuing introduction of said pressured gas and removing troducing pressured gas through said tubing while said tubing is being run to below said surface to gasify the liquid material and circulate same from the well prior to production testing of the well.

7. Method according to claim 6, said pressured gas being nitrogen.

8. Method according to claim 1, including hanging said small diameter tubing in place during said production testing.

Disclaimer 3,722,589.A7"thur W. Smith, Bay A. Plumme'r', and Uharles Wayne Johnson, all of Houston, Tex. WELL PRODUCTION TESTING AND FLOW CHARACTERISTIC EVALUATION METHODS USING SMALL DIAMETER TUBING. Patent dated Mar. 27, 1973. Disclaimer filed J an. 2, 1976, by the assignee, Big Three Industries, Inc.

Hereby enters this disclaimer to claim 1 of said patent.

[Ofiiciat Gazette March 16', 1.976.] 

1. Method for performing production testing of wells, comprising running a small diameter tubing down a well by means of a tubing injector apparatus, said tubing injector apparatus including a reel for storing the tubing wound thereon and having gas entrance means to said tubing at the hub of said reel, said tubing being run to below the surface of production entering the well from a reservoir, and production testing the well by injecting pressured gas into the production through said small diameter tubing to lift a portion of said production to the surface for recovery in uncontaminated condition.
 2. Method according to claim 1, said pressured gas being nitrogen.
 3. Method according to claim 1, including continuing introduction of said pressured gas and removing production from the well therewith for a time sufficient to determine flow characteristic evaluation of the well.
 4. Method according to claim 3, said pressured gas being nitrogen.
 5. Method according to claim 3, including hanging said small diameter tubing in place during said flow characteristic evaluation.
 6. Method according to claim 1, said well having liquid material therein above the surface of production entering the well from a reservoir, and including introducing pressured gas through said tubing while said tubing is being run to below said surface to gasify the liquid material and circulate same from the well prior to production testing of the well.
 7. Method according to claim 6, said pressured gas being nitrogen.
 8. Method according to claim 1, including hanging said small diameter tubing in place during said production testing. 